Whether you are dressing a tree or outlining the whole roofline, get the exact number of lights, strands, and the budget — before you buy a single box.
Total lights needed700
100-light strands7 strands
Estimated cost$48.93
LED tip:LED strands use about 90% less electricity than incandescent, stay cool to the touch, and one strand can safely connect 25–45 end-to-end (vs. about 5 for incandescent).
Assumptions: full tree ≈ 100 lights per foot of height; slim tree ≈ 75 per foot; roofline ≈ 10 lights per foot for a full festive look. Strands are standard 100-light sets.
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How to use the Christmas Light Calculator
1Pick tree or roofline mode
Decorating the tree? Enter its height and pick Full or Slim. Doing the house? Switch to roofline mode and enter the linear feet of eaves.
2Set your strand price
The default $6.99 matches typical LED mini-light strands. Adjust it to match what your local store charges.
3Shop with confidence
Hit Calculate My Lights for total lights, the number of 100-light strands, and your estimated cost — plus an LED vs. incandescent tip for your project.
Why the 100-lights-per-foot rule works
Pro decorators use it
About 100 lights per foot of tree height is the industry standard for a full, magazine-worthy look. Slim trees need about 75 per foot since there is less branch depth.
Roofline spacing solved
Ten lights per foot gives a rich roofline glow; wider spacing looks sparse and narrower spacing just burns budget.
Strand math matters
Strands only come in fixed lengths — rounding up to whole 100-light strands keeps you from buying half a box too few.
LED saves real money
LEDs draw roughly 90% less power than incandescent bulbs and last tens of thousands of hours, so a big display costs pennies a night to run.
Connect safely
You can string 25–45 LED strands end-to-end, but only about 5 incandescent ones. Never overload a circuit — the LED tip box adapts to your mode.
Christmas light questions, answered
How many Christmas lights do I need for my tree?
Plan on about 100 lights per foot of tree height for a full tree, or 75 per foot for a slim tree. A 7-foot full tree needs roughly 700 lights — seven 100-light strands.
How many lights do I need for my roofline?
Use about 10 lights per foot of roofline for a full festive look. Measure the linear feet of eaves you plan to outline — a 60-foot roofline needs around 600 lights.
Are LED or incandescent Christmas lights better?
LEDs win on almost every count: about 90% less electricity, cool to the touch, far longer lifespan, and much longer safe end-to-end chains. Incandescent bulbs still appeal to some for their warm vintage glow, but they cost more to run and need replacing more often.
How long is a 100-light strand of Christmas lights?
A standard 100-count mini-light strand spans roughly 20–22 feet (about 6 feet of lead wire plus the lighted length). Roofline C9 strands are typically sold by bulb count and spacing instead.
How much does it cost to light a house for Christmas?
It depends on size: a modest roofline of 60 feet needs about 6 strands at roughly $7 each, or about $42 plus clips and a timer. Bigger displays with trees, bushes, and lawn décor can run $150–$400 in lights alone.
How many strands can I connect end-to-end?
With LED strands, usually 25–45 strands safely, since each draws so little power. With incandescent, stop at about 5 strands — beyond that you risk tripped breakers or overheating. Always check the box for the exact rating.
How do I measure my roofline?
Measure the horizontal distance across the front of your house at the eaves with a tape measure, or pace it off and convert (an average adult stride is about 2.5 feet). Add 10% for ridges, peaks, and gutter dips.
